Video signals processed by a conventional apparatus, when redisplay on a monitor connected to a computer system, suffer several problems, such as false color at the edge of an image. Additionally, too high hardware cost inevitably lower the competitiveness of the apparatus. Another drawback of a conventional video signal processing apparatus lies in its comb filter. Conventional comb filters process video signals which are sampled on two adjacent horizontal scanning lines, without considering the resolution of vertical direction. The resolution of processed images is thus scarified.
H. Hagino, etc. in U.S. Pat. No. 5,523,798 describe a circuit for adjusting signal separation in Y/C separation comb filter by hardware connecting a phase-locked loop to a burst gate pulse generation circuit and multipliers. This greatly increases hardware costs. In addition, in separating a luminance signal and a chrominance signal, the comb filter of U.S. Pat. No. 5,523,798 takes only two dimensions into consideration. As a result of such two dimensional processing, the image processed suffers from false color and low resolution. Stuart S. Perlnan in U.S. Pat. No. 4,961,108 describes a circuit for comb filtering PAL and NTSC video signals. The comb filter of U.S. Pat. No. 4,961,108 also takes only two dimensions into consideration in processing video signals. Therefore, the problems of false color and low resolution can not be avoided.